Work machines such as wheel type loaders include work implements capable of being moved through a number of positions during a work cycle. Such implements typically include buckets, forks, and other material handling apparatus. The typical work cycle associated with a bucket includes sequentially positioning the bucket and associated lift arm in a digging position for filling the bucket with material, a carrying position, a raised position, and a dumping position for removing material from the bucket.
Control levers are mounted at the operator's station and are connected to an electrohydraulic circuit for moving the bucket and/or lift arms. The operator must manually move the control levers to open and close electrohydraulic valves that direct pressurized fluid to hydraulic cylinders which in turn cause the implement to move. For example, when the lift arms are to be raised, the operator moves the control lever associated with the lift arm hydraulic circuit to a position at which a hydraulic valve causes pressurized fluid to flow to the head end of a lift cylinder, thus causing the lift arms to rise. When the control lever returns to a neutral position, the hydraulic valve closes and pressurized fluid no longer flows to the lift cylinder.
In normal operation, the work implement is often abruptly started or brought to an abrupt stop after performing a desired work cycle function, which results in rapid changes in velocity and acceleration of the bucket and/or lift arm, machine, and operator. This can occur, for example, during a dumping operation when the bucket is moved to the end of its desired range of motion in a dumping position and the boom is quickly raised. This will impose excessive forces to the physical dump stops located on the boom.
These forces may damage the boom, as well as, damage the associated hydraulic circuitry that absorbs some of the shock that travels through the linkage assembly. This will likely increase maintenance and accelerated failure of the associated parts.
The present invention is directed to overcoming one or more of the problems as set forth above.